Generally, peripheral nerve stimulation is a neuromodulation technique in which electrical current is applied to a peripheral nerve. There are many applications of peripheral nerve stimulation, including: vagus stimulation for epilepsy, functional electrical stimulation for spinal cord injury, pudendal nerve stimulation for bladder control, hypoglossal nerve stimulation for sleep apnea, and peroneal nerve stimulation for food drop. Traditionally, electrical stimulation has been used in peripheral nerve stimulation.
Electrical stimulation employs a direct interface between a metal contact of a peripheral nerve electrode and the biological tissue. Depending on the current injected to the tissue through the metal contact, oxidation and reduction (“redox”) phenomena can occur at the neural interfaces. These redox phenomena can cause tissue damage and electrode corrosion, which limit the long-term use of electrical stimulation. Therefore, the amount of charge that can be used is strictly restricted for practical use. Additionally, the direct neural interface can act as a heat sink in magnetic resonance imaging (MRI) scanning machines, limiting MRI scanning for patients with implanted peripheral nerve electrodes.
Magnetic stimulation, which stimulates excitable tissue with an electric current induced by a time-varying magnetic field, is advantageous to electrical stimulation because it does not lead to redox phenomena or reduced MRI interference. In magnetic stimulation, there is no direct charge transfer between a metal electrode contact and the biological tissue. Instead, magnetic stimulation induces an electric current by an applied time-varying magnetic field. However, conventional magnetic stimulation requires a large inductor coil (e.g., many centimeters in size) that is not practical for implantation into the body.